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AB0347 (2026)
FINE-TUNING THE OPEN-SOURCE LARGE LANGUAGE MODEL MEDITRON SIGNIFICANTLY IMPROVES PERFORMANCE IN RHEUMATOLOGY
Keywords: Artificial Intelligence, Health services research
T. Hügle1, L. Campisi1, A. Dumusc1, F. J. Alromaih1, P. Cuenot1, C. Karatzios1, E. Shevroja1, M. A. Hartley2, G. Carra1, J. L. Raisaro1
1University Hospital Lausanne (CHUV) and University of Lausanne, Rheumatology, Lausanne, Switzerland
2École Polytechnique Fédérale de Lausanne EPFL, Computer Sciences, Lausanne, Switzerland

Background: Meditron is an open-source, large multimodal foundation model trained on medical data and has demonstrated performance comparable to currently available large language models (LLMs) [1]. For clinical applicability, expert evaluation and domain-specific fine-tuning of LLMs are essential. Collaborative co-design and evaluation frameworks enable efficient assessment and improvement of LLMs in real-world medical scenarios.


Objectives: To perform a comprehensive expert evaluation of Meditron and to fine-tune its knowledge in rheumatology using a collaborative LLM co-design platform.


Methods: Meditron3-70B [2] was evaluated using the Massive Open Online Validation & Evaluation (MOOVE) platform [3]. The dataset comprised 240 clinical questions used as prompts, covering immune-mediated rheumatic diseases, bone health, and musculoskeletal rehabilitation, and included 459 expert reviews of Meditron responses by six rheumatologists. Model performance was assessed using the following criteria: alignment with clinical guidelines, question comprehension, logical reasoning, relevance and completeness, harmlessness, fairness, contextual awareness, participant confidence, and model confidence. All criteria were rated on a 5-point Likert scale. The proportion of positively rated responses (score > 3) was calculated. Subsequently, 207 reviews were used to fine-tune the model. For comparative evaluation, the remaining 33 clinical questions were re-prompted to the base model (Meditron3-70B) and the fine-tuned model (now called CHUV-Meditron3-70B). Responses were independently reviewed by three rheumatologists in a head-to-head comparison.


Results: The MOOVE platform was considered easy to use for prompting, evaluation, and editing of model responses and provided an effective basis for fine-tuning. The proportion of positively rated responses varied across evaluation criteria. The highest scores were achieved for clarity (81.9%), communication (81.5%), and question comprehension (80.7%). Alignment with clinical guidelines was rated positively in 74.1% of cases, while logical reasoning achieved a positive rating of 76.6%. Harmlessness and fairness were rated positively in 76.6% and 80.3% of responses, respectively. Contextual awareness reached 73.7%, and model confidence 76.2%. The lowest positive ratings were observed for relevance and completeness (65.5%) and participant confidence in the responses (68.0%).

In direct comparison after fine-tuning, CHUV-Meditron3-70B outperformed the base model in 63.6% of cases, 9.1% of comparisons resulted in a tie, and 27.3% were won by the base Meditron3-70B model (Figure 1).


Conclusions: This study demonstrates both the potential and the necessity of domain-specific expert fine-tuning to improve LLM performance in rheumatology. While strengths were observed in comprehension and clarity, further improvements in relevance and completeness are required to support robust clinical applicability. Large-scale collaborative evaluation platforms represent a key element for the development of efficient, transparent, and safe LLMs for future clinical decision support.


REFERENCES: [1] Tam, T. Y. C. A framework for human evaluation of large language models in healthcare derived from literature review.

[2] Chen, Z. et al. MEDITRON-70B: Scaling Medical Pretraining for Large Language Models. Preprint at http://arxiv.org/abs/2311.16079 (2023).

[3] jointhemoove.org.


Acknowledgments: NIL.


Disclosure of Interests: Thomas Hügle Abbvie, J&J, GSK, others, Atreon, Fresenius Kabi, Lorenzo Campisi: None declared, Alexandre Dumusc: None declared, Fahad Jamal Alromaih: None declared, Paul Cuenot: None declared, Christos Karatzios: None declared, Enisa Shevroja: None declared, Mary-Anne Hartley: None declared, Giorgia Carra: None declared, Jean-Louis Raisaro: None declared.


DOI: annrheumdis-2026-eular.B.985
Keywords: Artificial Intelligence, Health services research
Citation: , volume 85, supplement 1, year 2026, page s1603
Session: Clinical research - Across diseases (Publication Only)